The inventive concepts relate to semiconductor memory, and more particularly, to nonvolatile memory modules including volatile memory devices and nonvolatile memory devices.
Semiconductor memory devices may be memory devices that are implemented by using semiconductors such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), etc. Semiconductor memory devices may be classified as volatile memory devices and/or nonvolatile memory devices.
Volatile memory devices may be memory devices which lose data stored therein when power is removed from the device. Volatile memory devices may include, for example, static random access memory (SRAM), dynamic RAM (DRAM), synchronous DRAM, etc. Nonvolatile memory devices may be memory devices which retain data stored therein even when power is removed from the device. Nonvolatile memory devices may include, for example, read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable and programmable ROM (EEPROM), flash memory devices, phase-change RAM (PRAM), magnetic RAM (MRAM), resistive RAM (RRAM), ferroelectric RAM (FRAM), etc.
Since the response and operation speed of DRAM can be fast, DRAM is often used as a main memory of a system. However, since DRAM is a volatile memory in which data may be lost when a power is shut off, a separate device may be used to retain data stored in the DRAM. In addition, since DRAM may store data by using capacitors, the size of a unit cell of DRAM may be large, thereby making it difficult to increase DRAM capacity when space is restricted.